The need for an accurate and sensitive means for monitoring the dose delivered by an ionizing radiation source or environment arises frequently. In the past, it has been observed that bombardment of a silicon-on-sapphire (SOS) n-channel MOS transistor with ionizing radiation gives rise to a "back-channel" leakage current I.sub.l. This current flows between drain and source in the silicon adjacent to the silicon-sapphire interface. Formation of the back channel has been previously attributed to radiation-induced positive charge buildup in the sapphire (Al.sub.2 O.sub.3) substrate near this interface. The increase in I.sub.l with ionizing dose can be as large as three to four orders of magnitude after a dose of 10.sup.3 to 10.sup.5 rads(Si). This increase will be observed if the device is irradiated with a typical value of drain-to-source voltage (V.sub.ds) applied, such as 10 V. The magnitude of the applied gate bias (V.sub.gs) during irradiation appears to be relatively unimportant in terms of affecting leakage current production.
A significant disadvantage of prior art dose monitors utilizing solid state devices is due to the fact that once they become irradiated they are not reusable. A need exists for an accurate ionizing radiation dose monitor which may be reused.